I'm usually generous when evaluating Shadowrun books, for a number of reasons, but even I noticed some problems with "War!"
From what I gather, this was originally supposed to be a generic supplement on how war is conducted in the Sixth World, but the concept was changed to that of a "story arc" book like Emergence and Ghost Cartels. Either of these would have been fine on its own, but it looks like the book that actually hit the shelves was a strange mix of both that does neither well.
The first half of the book is devoted to moving the Shadowrun metaplot forward by describing a war between Aztlan and Amazonia, something which has been hinted at for a while now. Unlike the previous titles mentioned above, which give you a broad timeline with a definite series of events, along with several adventures or adventure ideas for each major stage of the story, you get a handful of chapters that look like a big stream of conscience, with disorganized and somewhat redundant thoughts on the city ob Bogotá and what's going on in there. An actual description of the events that lead to the start of the war doesn't appear until chapter 2, and there are no maps at all. The authors themselves could have really used one, since there's no mention of Bogotá being right in the middle of the Andes mountains - it's instead described as being surrounded by jungle.
In the end, the feeling I got from reading this part of the book is that it went through no editing at all. I have no way of knowing whether this was actually the case, but it feels that way. Things are just sort of tossed together in there. You have a description of how the war starts, but not of how it ends (and no explicit indication that they intended to leave the end of the war for a future supplement). They mention it's a big war, and that fighting happens on lots of places along the border, but nothing outside of Bogotá is described. The Aztlan and Amazonian forces are given cursory descriptions. When you get to the descriptions of how wars are fought on the Sixth World, you get told they're basically the same as they were on the 20th century, despite all the high-tech and magic described in nearly every Shadowrun book.
There are /some/ passages here that are still good, like the one where they describe example shadowrunner teams that could be used as PCs or adversaries, but again, they don't seem to have developed much beyond the draft stage.
The "Global Hotspots" chapter is a better, with short, punchy vignettes about several other places around the world, each followed by 3-4 campaign or adventure ideas. I wouldn't have minded if the whole book had been written in this format. The brevity of each "hotspot" description leaves little room for factual errors or stream-of-conscience style rambling, so it's definitely an asset. Most of the campaign ideas are also pretty good!
Finally we get to the game information chapter, which is a bit of a mixed bag. It has information on how to run a mercenary/military campaign in the Sixth World, nothing how it differs from a standard "shadowrunners" game, which I guess is serviceable. There are also rules for post-traumatic stress disorders and when to ask for Composure tests during a war, which are fine. There's also a list of military gear, from load-bearing vests to nuclear warheads, which seems to suffer from some editing problems of its own if the forum discussions about it are anything to go by. Personally, I didn't pay much attention to it, as most of the gear and rules contained there already exist in GURPS, which is what I use to run my Shadowrun games.
All in all, I don't feel this is worth the price of purchase.